Insulated pipe structures are commonly used in heat distribution systems, where hot fluid or steam is distributed to a desired location, or in cryogenic applications. These systems can be used in residential or industrial applications such as for heating buildings or maintaining the temperature of a particular system. Such distribution systems are often installed underground and include a steel inner fluid carrying conduit surrounded by an insulating sleeve or jacket. The difficulty with this is that in most underground locations, water or dampness of some kind is present, which can damage the pipe apparatus over time. The water corrodes the steel fluid conduit and destroys the insulation's effectiveness in the system.
In one prior art pipe apparatus described in U.S. Pat. No. 3,677,303, an insulation sleeve surrounds an inner conduit which carries the heated fluid. The insulating sleeve and inner conduit are supported within a rigid, preformed casing by spacers which are located at intervals along the length of the sleeve, e.g. every nine feet, and which surround the sleeve circumferentially to support the insulation coaxially within the casing. The casing is formed from a pair of coaxially radially spaced plastic tubes. The spacers may include corrugated strips or be formed by rings which include holes in their surfaces. The voids between the corrugations allow air passage between unsupported sections of the insulation sleeve.
As seen in FIG. 5 of the above described patent, air spaces 83 formed by the corrugated support members 80 allow air to communicate between adjacent voids 82, forming a substantially continuous insulating air cavity throughout the length of the pipe. However, the voids created by the supporting members 80 are not of a continuous shape or constant cross-section along the length of the pipe between the insulated pipe and the outer casing, which is desirable not only for more complete venting, draining and drying, but also for air testing for structural and watertight integrity and detection of maintenance requirements.
Most prior art devices use steel conduit as a rigid outer casing, for purposes of enhanced strength. However, such devices do not provide protection from the corrosion of the casing and thus they allow the ingress of moisture through the exterior of the pipe apparatus to the insulation, destroying its effectiveness. Moisture may also come in contact with the inner fluid carrying conduit. If the inner conduit also corrodes in the presence of water, over time this conduit will be destroyed.
An object of the present invention is to provide an improved insulated pipe apparatus.
Another object of this invention is to provide an insulated pipe apparatus in which the possibility of moisture ingress is very low, thereby reducing the possibility of corrosion of an inner conduit.
Another object of this invention is to provide an insulated pipe apparatus with enhanced insulative properties and structural rigidity while providing access to its interior for facilitating venting, drying, and draining the insulating material and air testing for structural integrity and for detection of defects.
A further object of this invention is to provide means for sealing the ends of insulated pipe apparatus while providing for interconnection of a plurality of elongated voids which can be connected to external equipment.
Another object is to provide insulated pipe apparatus having improved provision for dissipation of heat from the inner conduit.